Growth Curves

Female Voiceover: One of the most powerful methods that we have for monitoring the well being of a child is a tool called growth monitoring. Growth monitoring is done all over the world. When we do growth monitoring, we are measuring three variables. So we're measuring firstly the weight of a child. That's usually recorded at birth, especially if there is a health professional with a scale nearby. Secondly we monitor the length or later when the baby is standing, the height of the baby. Finally we measure the head circumference. All of these variables together give us a sense of how that child is growing and how their overall health is. Two of these variables, the weight and the length, are usually put, at least in the United States, on the same curve. You can see that I'm drawing bands. This is a range of normal and each of these bands, the upper one represents length. So I'm going to write length on the y-axis here. Since we're in the US that would probably be measured in inches. The lower band, this band over here, also on the y-axis, is going to represent the weight of the child. Weight in pounds if we're in the US, in kilograms elsewhere in the world. Then on the x-axis we plot the age of the child. This would be birth and then a younger child's growth curve or growth chart usually goes up until 3 years of age and then their data gets put onto a different kind of growth curve. This would be 1 year of age. This would be 2 years of age. Let's just look at these bands and talk about those for a minute. So each of these bands has a middle line. That middle line is what we call the 50th percentile line. That means that about half of children will fall above that line and half will fall below, and similarly for length, we have a 50th percentile line. The upper line is usually the 95th percentile. That means that a child that falls on that line is taller than 95% of the children in that age group. Then the lowest line would be the 5th percentile. So here we have the 5th and the 95th. The key to these growth charts is that one data point doesn't really tell us much. Let's say we have a newborn who was born, let's say, on the lower end here of weight. Let's say normal range of weight would be between about 6 and 10 pounds for a newborn. Normal range of height would be between about 18 and 22 or 23 inches. Let's say that this child was born slightly on the lower side and maybe sort of at the 50th percentile for height. What we then need to do is as this child grows, with each visit to the doctor and in the US babies visit the doctor every two months usually at the beginning for the first six months. We would get a data point and it's not unusual in that first year for babies to cross percentile lines. Maybe this child would catch up and by one year of age this child would be right at the 50th percentile. Maybe this child's height would stay at the 50th percentile. But it gives us an overall picture. All of these data points put together give us an overall reassuring picture of the child's health because of the fact that they are growing along a nice smooth line. Now what if we had two 2-year-olds different children. Let's say one of them came in on Monday to see you and this 2-year-old was sort of weighing in at the 5th percentile. The other 2-year-old, and you haven't seen either of these children before, the other 2-year-old was, let's say at the 25th percentile. You might think, just looking at these two data points, that if we were going to be concerned about any of these children, we would be concerned about this one here because this child is right on the bottom line. What if I told you throughout this child's two years of life, this child had consistently tracked along the 5th percentile? Let's say this child's parents were small or there was another reason that this child was a small child but a healthy small child. Let's say in contrast that this child up here in purple, this child had let's say been born kind of on the heavier side and had been tracking along nicely along the 95th percentile line, and then let's say this child's weight had dropped off. Now this would be a very dramatic drop off. But I'm just trying to illustrate a point here. I'm going to move this one up a little bit because it probably wouldn't be so dramatic. But this kind of a drop off, a crossing of percentiles, especially nearing the second year of life, when usually children have sort of decided on which percentile they're going to stick to, that would be much more concerning than this child, even though this child is at a lower percentile. Now that doesn't mean to say that if we had two steady curves. Let's say the child in green versus the child in yellow, we would definitely be more concerned about the child in green, because of the fact that they're so far below the 5th percentile. Even though this is an even curve, a nice smooth curve of growth. The further below the lowest percentile, the greater our index of suspicion or our worry and yet we do need to have multiple data points in order to make a judgment about whether something is really going wrong with the child. Another thing to note here is that a drop off in weight is usually kind of an acute indicator. It's a sign that something has sort of gone wrong in the short term. Something like diarrheal disease would cause an acute fall off in weight. Only after long standing malnutrition, for example, will a child's height drop off. Let's say this child could have been tracking nicely along the 70th percentile and then let's say their height dropped off. Now this is a concerning trend because we're seeing a drop off in height and we call that growth stunting. Now why do we do this? Well, especially in developing countries, there are three reasons why growth monitoring is very important. Firstly it allows for a subtle reallocation of the family's resources. Even in poor families, when a child within the family is identified as being underweight for age, the family will often just ever so suddenly redistribute their income to support that child's nutrition. Secondly, if there are sources of external aid available to a community, growth monitoring and identification of children who are failing to thrive, or who are underweight for age, that will allow targeted distribution of that aid toward children who need it most. Finally, growth monitoring serves as a form of education for the community. It makes parents and caregivers aware of the importance of adequate nutrition in order for children to grow to be healthy. So I use the term failure to thrive and the abbreviation for that is FTT. Failure to thrive, it's the term that we use to describe a child who has a concerning profile on one of these growth monitoring charts. So for example, a child who is acutely falling off or a child who is growth stunted, and failure to thrive has two origins. Firstly we talk about organic failure to thrive. Organic failure to thrive occurs when there is something physiologically wrong with the child where they are unable to make use of the nutrients that they are taking into their body. Maybe they are unable to digest the nutrients or they are unable to absorb them, but for some reason the nutrients aren't getting to the tissues to help the body grow. The other kind of failure to thrive is called non-organic failure to thrive. The leading cause of non-organic failure to thrive is malnutrition due to poverty. In non-organic failure to thrive the child isn't getting access to nutritious foods to support the growth of that child.